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Determinación de la incertidumbre del método de análisis de aflatoxinas por HPLC en pasa de uva
Authors: Nora Dolores Martínez, Ana María Rodríguez, Aída Rosa Gutiérrez, Marina Daniela Di Carlo, Analía de los Ángeles Durán
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Objective: This work presents the definition of uncer-tainties for the methods of analysis of aflatoxins B1, B2, G1 and G2 in raisins by HPLC-FLD. The uncer-tainty of a method is one of the parameters required by the norm IRAM 301-ISO/IEC 17025:2005Stan-dard, applicable in the Argentine Republic and ac-credited by the Argentine Accreditation Organism (OAA), and forms part of the validation of analytical methods. In addition, it is a necessary requirement to expand the scope of accreditation of the Labora-tory of Analysis of Regional Products of Chemical Engineering (LAPRIQ, by the name in Spanish), be-longing to the Institute of Chemical Engineering of the National University of San Juan
Methodology: The procedure used is called “Bot-tom up”, based on a succession of calculation that take into account errors from each of the analyti-cal operations decomposed in primary activities. For the initial stage, sources of error that can affect the result of the analysis were identified. The Ishi-kawa’s fishbone procedure was used as a basis for determining the sources of error and their inciden-ce in the final uncertainty of the process. Once the factors that add up to the error in the measure-ment were defined, all the HPLC calibration tests were performed. Second, the combined uncertain-ties were added, weighted according to the impor-tance of their contribution through the sensitivity coefficient. Finally, the expanded uncertainty was determined using a coverage factor K = 2, which implies a confidence percentage of 95%. With this factor we can expect to include the largest fraction of the distribution of the values attributed to the measurand.
Results: Six sources of error were detected and co-rrespond, on the one hand, to the mass measure-ments of the sample, extraction volumes, elution, and aliquot for “clean up” and, on the other, HPLC detection and recovery rate of the method. The cal-culated uncertainties for the four aflatoxins are AFB1= 0.7 mg/kg, AFB2= 0.2 mg/kg, AFG1 = 0.9 mg/kg y AFG2 = 0.3 mg/kg.
Conclusions: The values of the expanded uncertain-ties are reported in the certificate of analysis, along with the result of the HPLC test, as one of the tests of the validation of the method validation.